   // define this class:
   class myStateValidityCheckerClass : public base::StateValidityChecker
   {
   public:
        myStateValidityCheckerClass(const base::SpaceInformationPtr &si) :
          base::StateValidityChecker(si)
           {
        }

        virtual bool isValid(const base::State *state) const
        {
                return ...;
        }
   };
   // or this function:
   bool myStateValidityCheckerFunction(const base::State *state)
   {
        return ...;
   }

   base::SpaceInformationPtr si(space);
   // either this call:
   si->setStateValidityChecker(base::StateValidityCheckerPtr(new myStateValidityCheckerClass(si)));
   // or this call:
   si->setStateValidityChecker(boost::bind(&myStateValidityCheckerFunction, _1));
   si->setStateValidityCheckingResolution(0.03); // 3%
   si->setup();
